1. Field of the Invention
The present invention relates to a sheet discharge device incorporated in a sheet processing device such as copying machine and printer as a part of the body of the processing device, and more particularly to an improvement of a sheet discharge device capable of commonizing an external unit such as a duplex unit and a sheet processing device using the same.
2. Description of the Prior Arts
An image forming device will be taken as an example of this type of a sheet discharge device. There has been conventionally known the one having an imaging engine including, for example, a photoreceptor drum and the like mounted in a body of an image forming device (body of a processing device) and provided with a sheet feeding device and a discharge tray in the body of the processing device, wherein a sheet transport path from the sheet feeding device to the discharge tray is formed at the imaging engine. In this device, an image is formed at the imaging engine with an electrophotographic system, whereupon the image formed by the imaging engine is transferred onto a sheet such as a paper and the like supplied from the sheet feeding device. Thereafter, the image is fixed onto the sheet by a fixing device, and then, the sheet having the image fixed thereon is discharged onto the discharge tray.
This type of the image forming device has a sheet discharge device incorporated therein at an outlet section of the body of the processing device.
A sheet discharge device conventionally used is the one having a pair of discharge rollers integrally incorporated therein at the outlet section of the fixing device unit.
Further, there has already been proposed a sheet discharge device provided with two discharge trays, i.e., upper and lower discharge trays, and discharged sheets are respectively distributed to be discharged onto the upper and lower discharge trays, in order to improve the accommodatable number of sheets in the discharge tray (for example, see Patent Reference 1).
[Patent Reference 1]
Japanese Published Unexamined Patent Application No. 2000-302311 (preferred embodiments of the invention, FIG. 1)
However, the sheet discharging position to the discharge tray is fixed to only one position in this type of the sheet discharge device, whereby the accommodatable number of the discharge sheet of the discharge tray is inevitably limited. Therefore, it is difficult for a user to change the accommodatable number of the discharge sheet.
For example, a technique disclosed in the Patent Reference 1 teaches a two-stage construction of the discharge tray, so that the accommodatable number of sheets is increased compared to the one having one-stage discharge tray, but it is impossible to change the respective accommodatable numbers of sheets of the respective discharge trays.
Therefore, the conventional technique has a technical problem that, if the user demands to remarkably increase the accommodatable number of sheets, an add-on large-capacity sheet stacking device has to be additionally mounted or the image forming device itself has to be changed to the type of large-capacity model.
Further, in order to add a duplex unit for performing a duplex recording to a sheet as an external unit, the sheet is required to be discharged in a direction different from the direction toward the discharge tray (normally, in the direction reverse to the direction toward the discharge tray), thereby entailing a technical problem that the external unit is required to have a different specification in the sheet discharge unit having a different specification.
With respect to these technical problems, it is considered that an adapter is respectively added to the external units. However, in this embodiment, a separate adapter is required every specification, thereby causing a fear that the construction of the device is likely to be complicated.